killed 30 others. just after the school issued an alert. university officials say they will appeal. the retail giant wal-mart, the biggest of them all is now fighting what could become the biggest civil rights class action case of them all, ever. one that may end up costing the company billions of dollars. today, the supreme court heard arguments on whether the lawsuit should go forward. at issue, whether a group of women, who claim discrimination, can sue on behalf of every woman who worked at any wal-mart store anywhere over the past decade. shannon bream is live outside the supreme court building. shannon, the case started with just one woman. how big could this get? >> well, betty dukes is that won one woman. her years at wal-mart were getting paid less than the men and getting passed over for promotions simply because she was a woman. she says it's time on behalf of the rest of the women at wal-mart. some put that at 500,000 women. some put it three times that high.